Conventionally, wireless communication systems (for example, CDMA2000 1xEV-DO and the like) for variably controlling downstream communication speeds (hereinafter, referred to as “downstream speeds”) according to a reception state in a communication terminal are known.
These wireless communication systems are wireless communication techniques in which a tradeoff between downstream speed, and error resilience by a plurality of modulation techniques, spread rates, and the like is possible and a higher communication speed can be provided according to the reception state of the communication terminal.
A communication terminal in this wireless communication technique measures the quality (carrier to interference ratio (CIR)) of a reception signal from the base station and requests the base station to provide the highest downstream speed estimated for successful data reception at an error rate equal to or below a predetermined level.
On the other hand, in response to requests of downstream speeds received from a plurality of communication terminals, the base station performs communication by performing scheduling and determining a communication terminal to which downstream communication information is to be transmitted.
Although telecommunication carriers can employ any desired technique for this destination determination scheduling, a scheduling algorithm called proportional fair is commonly employed.
This scheduling is a technique for balancing fairness of communication speeds of a plurality of subscribers and a maximized total throughput in the overall base station, and calculates a past average communication amount R (using the moving average or logarithmic mean and, in general, corresponding to the average of traffic over the past one second) for each communication terminal to assign downstream communication information to a communication terminal exhibiting the maximum of DRC/R serving as a ratio of a required downstream communication speed (DRC) to the above-described average communication amount (R) (for example, see Patent Document 1).
In a wireless communication system in which communication terminals communicate with a base station, the communication terminal sets a transmission power according to a reception state from the base station when the communication terminal receives the reception state from the base station and performs transmission, and then the transmission power of the communication terminal is controlled by control from the base station.
On the other hand, in a wireless communication system in which communication terminals communicate with a base station, a communication technique in which communication of a communication terminal located outside a communication area of the base station and the base station is possible by using a communication terminal located within the communication area of the base station as a relay station is known (for example, see Patent Document 2).    Patent Document 1: Japanese Patent Application Publication No. 2002-171287    Patent Document 2: Japanese Patent Application Publication No. 2003-309512